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Lovden M.,Karolinska Institutet | Lovden M.,Max Planck Institute for Human Development | Kohncke Y.,Karolinska Institutet | Laukka E.J.,Karolinska Institutet | And 7 more authors.

The integrity of the brain's white matter is important for neural processing and displays age-related differences, but the contribution of changes in white matter to cognitive aging is unclear. We used latent change modeling to investigate this issue in a sample of very old adults (aged 81-103. years) assessed twice with a retest interval of 2.3. years. Using diffusion-tensor imaging, we probed white matter microstructure by quantifying mean fractional anisotropy and mean diffusivity of six major white matter tracts. Measures of perceptual speed, episodic memory, letter fluency, category fluency, and semantic memory were collected. Across time, alterations of white matter microstructure in the corticospinal tract were associated with decreases of perceptual speed. This association remained significant after statistically controlling for changes in white matter microstructure in the entire brain, in the other demarcated tracts, and in the other cognitive abilities. Changes in brain volume also did not account for the association. We conclude that white matter microstructure is a potent correlate of changes in sensorimotor aspects of behavior in very old age, but that it is unclear whether its impact extends to higher-order cognition. © 2014 Elsevier Inc. Source

Persson J.,University of Stockholm | Persson J.,Umea Center for Functional Brain Imaging | Pudas S.,University of Stockholm | Pudas S.,Umea Center for Functional Brain Imaging | And 3 more authors.
Neurobiology of Aging

Age-related changes in the default-mode network (DMN) have been identified in prior cross-sectional functional magnetic resonance imaging studies. Here, we investigated longitudinal change in DMN activity and connectivity. Cognitively intact participants (aged 49-79years at baseline) were scanned twice, with a 6-year interval, while performing an episodic memory task interleaved with a passive control condition. Longitudinal analyses showed that the DMN (control condition > memory task) could be reliably identified at both baseline and follow-up. Differences in the magnitude of task-induced deactivation in posterior DMN regions were observed between baseline and follow-up indicating reduced deactivation in these regions with increasing age. Although no overall longitudinal changes in within-network connectivity were found across the whole sample, individual differences in memory change correlated with change in connectivity. Thus, our results show stability of whole-brain DMN topology and functional connectivity over time in healthy older adults, whereas within-region DMN analyses show reduced deactivation between baseline and follow-up. The current findings provide novel insights into DMN functioning that may assist in identifying brain changes in patient populations, as well as characterizing factors that distinguish between normal and pathologic aging. © 2014 Elsevier Inc. Source

Kalpouzos G.,Umea University | Kalpouzos G.,Umea Center for Functional Brain Imaging | Kalpouzos G.,Karolinska Institutet | Persson J.,University of Stockholm | And 2 more authors.
Neurobiology of Aging

Functional brain imaging studies of normal aging typically show age-related under- and overactivations during episodic memory tasks. Older individuals also undergo nonuniform gray matter volume (GMv) loss. Thus, age differences in functional brain activity could at least in part result from local atrophy. We conducted a series of voxel-based blood oxygen level-dependent (BOLD)-GMv analyses to highlight whether age-related under- and overrecruitment was accounted for by GMv changes. Occipital GMv loss accounted for underrecruitment at encoding. Efficiency reduction of sensory-perceptual mechanisms underpinned by these areas may partly be due to local atrophy. At retrieval, local GMv loss accounted for age-related overactivation of left dorsolateral prefrontal cortex, but not of left dorsomedial prefrontal cortex. Local atrophy also accounted for age-related overactivation in left lateral parietal cortex. Activity in these frontoparietal regions correlated with performance in the older group. Atrophy in the overrecruited regions was modest in comparison with other regions as shown by a between-group voxel-based morphometry comparison. Collectively, these findings link age-related structural differences to age-related functional under- as well as overrecruitment. © 2012 Elsevier Inc. Source

Salami A.,Umea Center for Functional Brain Imaging | Salami A.,Umea University | Eriksson J.,Umea Center for Functional Brain Imaging | Eriksson J.,Umea University | And 3 more authors.
Biochimica et Biophysica Acta - Molecular Basis of Disease

Aging is associated with declining cognitive performance as well as structural changes in brain gray and white matter (WM). The WM deterioration contributes to a disconnection among distributed brain networks and may thus mediate age-related cognitive decline. The present diffusion tensor imaging (DTI) study investigated age-related differences in WM microstructure and their relation to cognition (episodic memory, visuospatial processing, fluency, and speed) in a large group of healthy subjects (n. = 287) covering 6 decades of the human life span. Age related decreases in fractional anisotropy (FA) and increases in mean diffusivity (MD) were observed across the entire WM skeleton as well as in specific WM tracts, supporting the WM degeneration hypothesis. The anterior section of the corpus callosum was more susceptible to aging compared to the posterior section, lending support to the anterior-posterior gradient of WM integrity in the corpus callosum. Finally, and of critical interest, WM integrity differences were found to mediate age-related reductions in processing speed but no significant mediation was found for episodic memory, visuospatial ability, or fluency. These findings suggest that compromised WM integrity is not a major contributing factor to declining cognitive performance in normal aging. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease. © 2011 Elsevier B.V. Source

Kompus K.,Umea Center for Functional Brain Imaging | Kompus K.,Umea University | Kompus K.,University of Bergen | Kalpouzos G.,Umea Center for Functional Brain Imaging | And 3 more authors.
Brain Research

Functional lateralization of episodic memory processes in the frontal lobe is an area of intense study in the field of cognitive neuroimaging. Yet, to date there is insufficient knowledge of what role the interhemispheric structural connectivity plays in this lateralized organization. We analyzed functional and structural magnetic resonance imaging data from healthy adult volunteers who performed an associative encoding and retrieval task. We examined the relationship between functional voxel-based relative asymmetry of encoding and retrieval in the frontal lobes and the size of the anterior corpus callosum (antCC; corrected for brain size). The size of the antCC was strongly associated to the relative encoding-retrieval asymmetry in the ventrolateral prefrontal cortex (BA 47). These findings show that the functional asymmetry of episodic memory processes in the frontal lobes is associated with the structural connectivity between the hemispheres. © 2011 Elsevier B.V. All rights reserved. Source

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